 Both the M- and S-class submarines were sold to China, and two more M-XV series of this class ("M-278" and "M-279") were sold to China a few years later.Those purchased by China were renamed, but the two leased "Shchuka"-class submarines were not.The four M-class submarines bought by China were renamed National Defense # "21", "22", "23" (ex "M-278") and "24" (ex "M-279") respectively.